The invention relates generally to generating codes for use in layered space-time architectures.
Unlike the Gaussian channel, the wireless channel suffers from multi-path fading. In such fading environments, reliable communication is made possible only through the use of diversity techniques in which the receiver is afforded multiple replicas of the transmitted signal under varying channel conditions.
Recently, information theoretic studies have shown that spatial diversity provided by multiple transmit and/or receive antennas allows for a significant increase in the capacity of wireless communication systems operated in Rayleigh fading environment. Two approaches for exploiting this spatial diversity have been proposed. In the first approach, channel coding is performed across the spatial dimension, as well as the time, to benefit from the spatial diversity provided by using multiple transmit antennas. The term xe2x80x9cspace-time codesxe2x80x9d is used to refer to this coding scheme. One potential drawback of this schemes is that the complexity of the maximum likelihood (ML) decoder is exponential in the number of transmit antennas. A second approach relies upon a layering architecture at the transmitter and signal processing at the receiver to achieve performance asymptotically close to the outage capacity. In this xe2x80x9clayeredxe2x80x9d space-time architecture, no attempt is made to optimize the channel coding scheme. Further, conventional channel codes are used to minimize complexity. Accordingly, a need exists for a layering architecture, signal processing, and channel coding that are designed and optimized jointly.
The disadvantages of existing channel coding methods and receivers for multiple antenna communication systems are overcome and a number of advantages are realized by the present invention which provides space-time codes for use in layered architectures having arbitrary numbers of antennas and arbitrary constellations. Algebraic designs of space-time codes for layered architectures are provided in accordance with the present invention.
In accordance with an aspect of the present invention, rate k/n convolutional codes are provided for layered space-time architectures (e.g., rates higher than or equal to 1/n where n is the number of transmit antennas).
In accordance with another aspect of the present invention, convolutional codes for layered space-time architectures are generated using matrices over the ring F[[D]] of formal power series in variable D.